The view of galaxy formation from Hawaii: Seeing the dark side of the universe

Abstract

The strength of the submillimeter background light shows directly that much of the energy radiated by star formation and AGN is moved to far infrared wavelengths. However, it is only as this background at 850 microns has been resolved with direct submillimeter imaging that we have seen that it is created by a population of ultraluminous (or near ultraluminous) infrared galaxies (ULIGs) which appear to lie at relatively high redshifts (z>1). Mapping the redshift evolution of this major portion of the universal star formation has been difficult because of the poor submillimeter spatial resolution, but this difficulty can be overcome by using extremely deep cm continuum radio observations to obtain precise astrometric information since the bulk of the brighter submillimeter sources have detectable radio counterparts. However, with this precise position information available, we find that most of the submillimeter sources are extremely faint in the optical and near infrared (I>>24 and K=21-22) and inaccessible to optical spectroscopy. Rough photometric redshift estimates can be made from combined radio and submillimeter energy distributions. We shall refer to this procedure as millimetric redshift estimation to distinguish it from photometric estimators in the optical and near IR. These estimators place the bulk of the submillimeter population at z=1-3, where it corresponds to the high redshift tail of the faint cm radio population. While still preliminary, the results suggest that the submillimeter population appears to dominate the star formation in this redshift range by almost an order of magnitude over the mostly distinct populations selected in the optical-ultraviolet.